A plate heat exchanger of the above mentioned kind is known through GB 1 500 917. The previous known plate heat exchanger is provided with a cover of rubber material or similar which is moulded around the plate heat exchanger to prevent leakage to flow out to the surrounding atmosphere.
Plate heat exchangers, used at high temperatures, often require frequent gasket replacement, owing to hardening of the gaskets, which deteriorates the sealing ability. Mostly it is the influence from the oxygen in surrounding air in connection with heightened temperature, which causes the breaking down of the rubber material. The choice of heat transfer fluid in the plate heat exchanger is of minor importance. If the gaskets are protected, so that they will not contact the surrounding air during operation, a considerable increase of life at high temperatures can be attained.
One way to achieve this could be to locate the plate heat exchanger in a hermetic container. Such a container could become very expensive, in particular for larger plate heat exchangers. An additional problem with a hermetic container for a plate heat exchanger is that a hydrostatic test and inspection must be allowed. This means that the container must be able to be assembled and dismantled on a plate heat exchanger already tightened.
To embed the package of heat transfer plates, as proposed in GB 1 500 917, does not solve the problem sufficiently. A moulded cover cannot be dismantled in a simple way and besides the cover will assume a rather high temperature and thus aging in the same way as the rubber gaskets. A cover must also function and seal properly despite huge deflection of the end plates during operation, which a moulded cover does not.